What do we know about soil carbon destabilization?

Most empirical and modeling research on soil carbon (C) dynamics has focused on those processes that control and promote C stabilization. However, we lack a strong, generalizable understanding of the mechanisms through which soil organic carbon (SOC) is destabilized in soils. Yet a clear understandi...

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Bibliographic Details
Published in:Environmental research letters 2019-08, Vol.14 (8), p.83004
Main Authors: Bailey, Vanessa L, Pries, Caitlin Hicks, Lajtha, Kate
Format: Article
Language:English
Subjects:
bioavailability
Biological activity
Bioturbation
Birch effect
Carbon
Changing environments
Colloiding
Colloids
Destabilization
Drying
ENVIRONMENTAL SCIENCES
Freeze thaw cycles
Freeze-thawing
Metabolism
Microorganisms
Minerals
Mycorrhizas
Occlusion
Organic carbon
Organic soils
physical occlusion
Priming
Soil dynamics
Soil environment
soil organic carbon
Soil stabilization
Soils
Stabilization
Tillage
Wetting
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Summary:Most empirical and modeling research on soil carbon (C) dynamics has focused on those processes that control and promote C stabilization. However, we lack a strong, generalizable understanding of the mechanisms through which soil organic carbon (SOC) is destabilized in soils. Yet a clear understanding of C destabilization processes in soil is needed to quantify the feedbacks of the soil C cycle to the Earth system. Destabilization includes processes that occur along a spectrum through which SOC shifts from a 'protected' state to an 'available' state to microbial cells where it can be mineralized to gaseous forms or to soluble forms that are then lost from the soil system. These processes fall into three general categories: (1) release from physical occlusion through processes such as tillage, bioturbation, or freeze-thaw and wetting-drying cycles; (2) C desorption from soil solids and colloids; and (3) increased C metabolism. Many processes that stabilize soil C can also destabilize C, and C gain or loss depends on the balance between competing reactions. For example, earthworms may both destabilize C through aggregate destruction, but may also create new aggregates and redistribute C into mineral horizon. Similarly, mycorrhizae and roots form new soil C but may also destabilize old soil C through priming and promoting microbial mining; labile C inputs cause C stabilization through increased carbon use efficiency or may fuel priming. Changes to the soil environment that affect the solubility of minerals or change the relative surfaces charges of minerals can destabilize SOC, including increased pH or in the reductive dissolution of Fe-bearing minerals. By considering these different physical, chemical, and biological controls as processes that contribute to soil C destabilization, we can develop thoughtful new hypotheses about the persistence and vulnerability of C in soils and make more accurate and robust predictions of soil C cycling in a changing environment.
ISSN:1748-9326
1748-9326
DOI:10.1088/1748-9326/ab2c11